Early detection and diagnosis are key for successful treatment of cancer such as breast cancer. Conventional X-ray mammography has been shown a cost-effective tool for early detection of breast cancer. However, the predictive value and specificity of X-ray mammography are limited due to projecting a three-dimensional anatomy into a two-dimensional image and due to poor contrast detectability. The minimum human cancer size that can be detected by conventional X-ray mammography has been on the order of 10 mm in diameter, weighing on the order of 1 gram and containing about 109 cells. If the cancer starts from a single cell, it will undergo about 10 volume doubling times to reach a size of 10 mm in diameter. Ten further volume doubling times will lead to a tumor weighing about 1 kg with a size of 8-10 cm in diameter, which may be lethal. Currently only the latter 10 doubling times are typically observable in human. There is a need for a non-invasive procedure to explore the initial 10 doubling times since an initial latency period is believed to be followed by a rapid, exponential growth period that finally leads to a lesion with a size of about 10 mm in diameter, where the growth rate begins to decrease.
Gadolinium (Gd) contrast agents have been used with magnetic resonance imaging (MRI) in detection of breast cancer to enhance image contrast by detecting the Gd uptake in the cancer lesions and its washout profiles over time which are more sensitive than those of benign structures or lesions. Gd contrast-enhanced MRI has high sensitivity and can detect many breast cancer lesions missed or occult by conventional compression X-ray mammography. However Gd-MRI suffers from low specificity with many false positive findings, where a benign tissue is incorrectly identified as malignant. This is a problem shared with conventional compression X-ray projection mammography where about 75 percent of the biopsies of mammogram-identified suspicious regions turn out to be benign.
Cone beam CT has been used to provide three-dimensional images of patients' breasts. One problem with conventional cone beam CT is that the cancer lesions in the breast have about the same X-ray absorption coefficient and contrast level in CT slice images as the benign glandular tissue, which makes it difficult to differentiate the malignant lesions from benign structures, especially when the malignant lesions are adjacent to or combined with the glandular tissue. This is particularly a problem in younger women with denser breasts that are comprised heavily of glandular tissue.
Accordingly, there is a need for improved methods and systems for early detection, diagnosis and treatment of cancer throughout the bodies of humans or animals with high spatial and time resolutions.